1. Field of the Invention
This invention relates generally to the storage of hydrogen in containers and, more specifically, to an apparatus and a method for a hydrogen storage system that contains porous materials that can adsorb or absorb hydrogen.
2. Description of the Related Art
There is great interest in hydrogen as a replacement for fossil fuels because of its very high energy density per unit weight, because it is readily available through the electrolysis of water, and because it is a virtually pollution-free energy source. Some major drawbacks to the use of hydrogen as fuel are that it is extremely volatile and that it is difficult to store.
In developing hydrogen fuel systems for the so-called hydrogen economy, a lot of attention has been focused on methods and systems for economical storage and distribution of quantities of hydrogen suitable for use as a fuel in micro-power plants, in vehicles and in personal electronics. There will be a need to store hydrogen as inventory at the point of production; there will be a need to store hydrogen for transport from producers to distributors; there will be a need to store hydrogen at the point of distribution; and there will be a neet to store hydrogen at the point of use. For all these storage applications, it will be necessary to store hydrogen safely in the smallest possible volumes. Certainly for vehicles and for personal electronics, it will also be necessary to store hydrogen at the lowest possible weight. At present, there are four major methods of hydrogen storage that are being discussed. Some are already in use; some are still in the testing stage.
One method is to use high pressure tanks to store hydrogen at pressures as high as 10,000 psi. One of the problems with this method is that highly-reactive hydrogen is a good diffuser, and even more so under high pressure. Many tank materials cannot stand up to hydrogen diffusion at high pressures for a long period of time. When lightweight storage is added to the requirements, it is not really possible to make a robust high-pressure storage tank for power applications.
Another hydrogen storage method involves using metal hydrides, such as magnesium-based alloys, to bind to hydrogen. Although this method does not require high pressure and can even work at room temperature, there are other drawbacks. The metal hydrides are generally heavier than the hydrogen gas by a factor of about 10. When hydrogen is released, some metal contamination goes with it, which is undesirable. Metal hydride storage is not very energy efficient. It can use up as much as half the energy of the stored hydrogen just to extract the hydrogen from the metal hydride. Metal hydride storage has been disclosed by Liu et al. in U.S. Pat. No. 4,358,316, by Bernauer et al. in U.S. Pat. No. 4,446,101, and by Ovshinsky et al. in U.S. Pat. No. 6,328,821.
Liquid hydrogen storage at cryogenic temperatures is being used in some applications. This method is rather cumbersome and unreliable as it requires using a second cryogenic liquid, such as liquid nitrogen, and it is necessary to maintain the temperature at 20K to avoid boil off of hydrogen.
Activated carbon has been used to store hydrogen at cryogenic temperatures and moderate pressures (50-70 atm), as has been described by Schearz in U.S. Pat. No. 4,716,736. Cryogenic storage in activated carbon can be done at a higher temperature (80K) than is required for liquid hydrogen storage. Hydrogen can bind to the surfaces in the activated carbon and can be released by increasing the temperature. Often activated carbon is not very pure, and contaminants are released with the hydrogen. Many researchers have found that it is difficult to get activated carbon to release all of its stored hydrogen. Problems cited with activated carbon include low weight percent storage capacity and maintaining cryogenic temperatures. Some of these problems have been discussed by Hynek et al. in xe2x80x9cHydrogen storage by carbon sorption,xe2x80x9d Int. J. Hydrogen Energy, Vol. 22, No. 6, pp.601-610, 1997.
Other materials for hydrogen storage that are being explored include carbon nanotubes and graphite fibers. These have been described by Rodriguez et al. in U.S. Pat. No. 5,653,951 and U.S. Pat. No. 6,159,538.
Clearly the requirements for hydrogen storage in the hydrogen economy have not been met. There is a need for a system that can store and supply significant quantities of hydrogen at higher temperatures and lower pressures than those used by the current methods.
In accordance with one embodiment of the present invention, a hydrogen storage and supply apparatus is provided. The apparatus has container that includes a cold enclosure. A porous material capable of occluding hydrogen pervades the cold enclosure. The porous material contains a plurality of light elements including Be, B, C, N, O, F, Mg, P, S, Li, Na, Al, Si and Cl. The cold enclosure may have a temperature in a range between about 30K and 270K, preferably between about 100K and 250K, and, more preferably, between about 150K and 220K. The container can withstand pressures up to about 50 bara, preferably, between about 2 bara and about 20 bar. The container may have a layered wall structure with at least two walls. There can be a cavity between the walls, which can provide thermal insulation. There may be at least one port in the container, which provides a channel for hydrogen flow into or out of the cold enclosure. The port may contain at least one valve to control the hydrogen flow. In some arrangements, there can be one or more hydrogen storage and supply apparatuses that are engaged with a coupling assembly through the ports on the containers. Hydrogen may be either provided to or withdrawn from the containers through the coupling assembly.
In accordance with another embodiment of the invention a hydrogen-consuming system is provided. The system has a container with a cold enclosure. A porous material capable of occluding hydrogen pervades the cold enclosure. The porous material contains a plurality of light elements including Be, B, C, N, O, F, Mg, P, S, Li, Na, Al, Si and Cl. On the container, there is at least one port that provides an outlet for hydrogen flow from the cold enclosure associated with the container. A hydrogen-fueled device is connected to the container at the port so that the device can receive hydrogen from the cold enclosure. In some arrangements, the containers are interchangeable. The hydrogen-fueled device may be a fuel cell. The hydrogen-consuming system may be a transportation vehicle, a household appliance, or an electronic appliance.
In another aspect of the invention, a hydrogen production and distribution system is provided. The system includes one or more hydrogen production facilities, a hydrogen distribution system that transfers hydrogen from the production facilities to points of hydrogen consumption. Hydrogen storage apparatuses, as described above, are used in any part of the hydrogen distribution system.
In other embodiments, methods for storing and supplying hydrogen are provided. The method involves providing at least one container having a cold enclosure and at least one port, and placing a porous material capable of occluding hydrogen in the cold enclosure. The material is as described above. Hydrogen is provided to the porous material in the cold enclosure. Hydrogen can be allowed to flow out from the cold enclosure through the port. A coupling assembly can engage one or more containers, and hydrogen can be provided to or withdrawn from the containers through the assembly.
In another aspect of the invention, a method for using hydrogen as fuel is provided. The method involves providing at least one container with a cold enclosure and porous material as described above. A channel for hydrogen flow out from and into the cold enclosure is provided by fitting the container with at least one port. Hydrogen is stored in the porous material in the cold enclosure. A hydrogen-fueled device is connected to the port on the container, and hydrogen is allowed to flow out from the cold enclosure to the hydrogen-fueled device. The hydrogen-fueled device may be a fuel cell and/or a component of a machine.
Further features and advantages of the present invention will become apparent to those of ordinary skill in the art in view of the detailed description of preferred embodiments below, when considered together with the attached drawings and Claims.